Patent Document 1 discloses a forming method for a hard coating, which enables forming a hard coating on the surface of a base by cold state strain-induced transformation. The hard coating forming method is to spray solid metal powder onto the surface of the base with compressed gas as a medium so as to form the hard metal coating. In the forming method, the metal powder is made of a metal material that can cause processing-induced transformation, which is slammed into the base at such a high speed that causes processing-induced transformation so that it is plastically deformed into a fiat shape and deposited to layers on the surface of the base while it also causes processing-induced transformation of the previously deposited metal powder. In this way, the forming method is characterized in that the metal coating to be formed on the surface of the base is harder than the metal powder that has not been slammed into the base yet.